Physiological parameter sensors can perform a wide variety of functions including but not limited to detecting: pulse, saturated oxygen content of blood, blood pressure, body temperature, blood analyte concentrations, respiratory gas concentrations, and breathing rates. Physiological parameter sensors can take a wide variety of forms depending on the size and species of a body being measured, the area of the body being sensed and the type of sensing being conducted. Pulse oximetry sensing measures the saturated oxygen content of arterial blood. Pulse oximetry sensors can be positioned on fingers, toes, ear lobes, and also on flatter body parts such as the forehead or chest. In order to fit various body parts, pulse oximetry sensors are produced in a wide variety of forms. Capnography sensors measure the amount of CO2 in respiratory gases. Normally a body is fit with a re-breather type of face mask or a nasal cannula. Some of these sensor forms require correct positioning in order to ensure proper functioning. Existing physiological parameter sensor systems do not provide automatic sensing of the presence, position, location, size, or movement of a body part. In modern clinics and hospitals many physiological parameter parameters are measured remotely, and a sensor alarm indicating that the sensor has moved or slipped out of position would be very useful. A sensing system with the ability to indicate a presence of a body part in a sensor and a correct position of the body part relative to the sensor would provide increased accuracy and improved functioning. In addition, sensing of the position of a body part relative to the sensor could be used to provide feedback to the user to obtain optimal sensor placement.